The present invention relates to an image processing system, projector, program, information storage medium and image processing method which can correct the distortion of an image.
When an image is projected by an image projection device such as a projector and if the optical axis of the projected light is not coincident with a projection target such as a screen, the projected image may be distorted to create a so-called keystone distortion from image distortions in the vertical and horizontal directions.
For such a reason, the image projection device must project a proper image after the distortion has been eliminated.
However, the general image projection device having an image distortion correcting function includes an inclination sensor which can correct the image distortion in the vertical direction, but not the image distortion in the horizontal direction.
In order to correct the distortion in the horizontal direction, a user must indicate four corner points in a screen by use of a mouse or the like so that the image projection device can semi-automatically correct the image distortion in the horizontal direction, based on the user's indications. It is troublesome for the user to indicate the four corner points in the screen through the mouse or the like.
To solve such a problem, for example, Japanese Patent Laid-Open Application No. 2001-61121 has proposed a projector device which comprises a projection plane capturing means for capturing the shape of the projection plane by associating coordinates of the projector's image with coordinates of the camera's image based on an image taken by a camera, the taken image being projected when a pattern image is displayed, and determining three-dimensional coordinate of the position where the pattern image is projected through triangulation, and an image correction means for performing corrections for inclination and magnification in the original inputted image according to the sensed shape of the projection plane.
Japanese Patent Laid-Open Application No. 2001-61121 also describes that a known three-dimensional shape measuring device can be used as projection plane capturing means and that the projection plane sensing means are not essential for the invention thereof.
However, the known three-dimensional shape measuring device requires two cameras, for example, when the triangulation is to be carried out. This makes the structure complicated and increases the manufacturing cost.
Additionally, such a technique of detecting the shape of the projection target such as a screen to process the image as in the Japanese Patent Laid-Open Application No. 2001-61121 cannot be applied to a wall. Thus, projection targets to which such a technique can be applied will be limited.